Talos Vulnerability Report

TALOS-2018-0748

April 25, 2019

CVE Number

CVE-2018-4063

Summary

An exploitable remote code execution vulnerability exists in the upload.cgi functionality of Sierra Wireless AirLink ES450 FW 4.9.3. A specially crafted HTTP request can upload a file, resulting in executable code being uploaded, and routable, to the webserver. An attacker can make an authenticated HTTP request to trigger this vulnerability.

Tested Versions

Product URLs

CVSSv3 Score

9.9 - CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CWE

CWE-434: Unrestricted Upload of File with Dangerous Type

Details

Sierra Wireless is a wireless communications equipement designer and manufacturer. They provide both embedded solutions as well as wireless hardware solutions, including both the ES450 and GX450 devices. The AirLink ES450 is a LTE gateway designed for distributed enterprise. The ES450 is typically seen connecting Point-of-sale devices, remote SCADA equipment, or other business critical equipment. The AirLink ES450 also provides a terminal server for remote out-of-band administration.

ACEManager is the web server included with the AirLink ES450. This web server is responsible for the majority of interactions in the device. Some specific capabilities of the web server are routing, device reconfiguration, user authentication and certificate management. The vendor has stated that the ACEManager web application is not accessible by default from the Cellular WAN.

This vulnerability exists in the file upload capability of templates within the AirLink 450. When uploading template files, you can specify the name of the file that you are uploading. There are no restrictions in place that protect the files that are currently on the device, used for normal operation. If a file is uploaded with the same name of the file that already exists in the directory, then we inherit the permissions of that file. In this case, the files that exist in the directory that the template file is saved to are:

fw_expected_rm.cgi

fw_status.cgi

fw_upload_init.cgi

fw_upload_init.sh

rm_switching_action.cgi

These files all have executable permissions on the device. By uploading a small wrapper, we can upload arbitrary code to the device and run by simply navigating to the web page through the browser. Since ACEManager is running as root any executables run will be running also as root. The following request shows a basic file upload to show running permissions.